I think I ran into a bug in zexy's lister, or at least a surprising behavior that should perhaps be documented. It seems that its output is reevaluated for each inlet it is connected to (ie if the left inlet of the lister has changed in between because of the depth-first traversal, its output will change). I suppose it's a bug because the [f] object doesn't behave this way. I'm not sure my explanations are very clear, so I attached a small patch to demonstrate the issue.